LONG-TERM EXPOSURE TO AIR POLLUTION (PM 2.5 AND NO 2 ) AND MORTALITY: RESULTS OF THE ROME LONGITUDINAL STUDY (ROLS)

Abstract

Background and aims: There are few longitudinal studies evaluating the role of chronic exposure to air pollutants within the same urban setting. We analyzed the association of long-term exposure to PM2.5 and NO2 with mortality in a large cohort. Methods: The Rome Longitudinal Study is a fixed cohort enrolled at the 2001 census. We selected subjects aged 45-80 years at the baseline who had not changed their address in the previous five years (n=684,204). Exposure at residence to PM2.5, was predicted by means of a chemical transport model (FARM) (1 km2 grid) using 2005 emissions data. Spatial levels of NO2 were derived from a specific land use regression model (R2=0.66). We had information on age, gender, education, occupation, place of birth, and area-based socioeconomic position at baseline. All subjects were followed till December 31, 2006. Cox regression models were used to study the association between the exposure and cause-specific mortality, taking several confounders into account. Results: During the study period, 45,006 natural deaths occurred (33% cardiovascular, 5% respiratory disorders, 3.3% diabetes, and 12% lung cancer). The average exposure was 23 (sd 4) μg/m3 for PM2.5 and 44 (8) μg/m3 for NO2. The correlation of the two exposure indicators was 0.75. With increased exposure of PM2.5 and NO2 there was an increased risk of dying for natural causes: 7% (95%CI:4%-9%) for 10μg/m3 increase of PM2.5, and 9% (95%CI:6%-13%) for 10μg/m3 increase of NO2. The relationships were linear with no evidence of a threshold. The strongest associations were found for cardiovascular diseases and diabetes. Conclusions: This is one of the largest European urban cohort study on PM2.5. The results indicate that long-term exposures to PM2.5, and NO2 at residence are associated with mortality in Rome and the effect estimates are very similar to what has been suggested in studies from the USA.